Unraveling the influence of non-fullerene acceptor molecular packing on photovoltaic performance of organic solar cells

摘要

In non-fullerene organic solar cells, the long-range structure ordering induced by end-group -pi stacking of fused-ring non-fullerene acceptors is considered as the critical factor in realizing efficient charge transport and high power conversion efficiency. Here, we demonstrate that side-chain engineering of non-fullerene acceptors could drive the fused-ring backbone assembly from a pi-pi stacking mode to an intermixed packing mode, and to a non-stacking mode to refine its solid-state properties. Different from the above-mentioned understanding, we find that close atom contacts in a non-stacking mode can form efficient charge transport pathway through close side atom interactions. The intermixed solid-state packing motif in active layers could enable organic solar cells with superior efficiency and reduced non-radiative recombination loss compared with devices based on molecules with the classic end-group pi-pi stacking mode. Our observations open a new avenue in material design that endows better photovoltaic performance. Non-fullerene acceptors are crucial for realising efficient charge transport and high power conversion in organic solar cells, yet the relationship of molecular packing and carrier transport is not well-understood. Here, the authors study the effect of side-chain engineering on the backbone assembly and the corresponding charge transport pathway.

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